In this project chemically reactive and water soluble macromolecules have been synthesized and their effects on mammalian cells in culture studied, the main emphasis being on the study of their interaction with cell membrane. Polysaccharides, dextran and inulin, which are neither bound nor consumed by cells, were used as carriers for various chemically reactive groups. The resulting macromolecules have been tested in vitro on mouse erythroleukemic cells, on human fibroblast and on human lymphocytes. In addition to previously prepared and studied compounds the following new reactive groups were used: a) Sulfhydryl groups, which are reducing agents for the surface of cells and furthermore bind to exposed cysteine residues and thus lead to a coating of cells with polysaccharides. Furthermore, sulfhydryl substituted macromolecules were used for chemical attachment of the drugs which contained allyl groups to polysaccharide carriers. b) Residues of detergent Triton X-100 - the resulting polysaccharide derivatives were used as mild acting surfactants in the permeabilization of cells in vitro.